1. Field of the Invention
The present invention relates to a control device for controlling a feed roller to feed a sheet of paper, or other sheet-like or plate-shaped medium, in a copy machine or a printer.
2. Description of the Related Art
Control devices are provided in printers, copy machines, and the like for controlling feed rollers such as those for feeding sheets of paper or other sheet-like or plate-shaped mediums. Such control devices usually work in association with one or more sensors disposed either upstream or downstream from the feed roller. The sensor is for detecting passage of sheets. The controller determines whether sheet feed is being correctly performed according to detection by the sensor. One type of sensor detects movement of sheets when mechanically displaced by the presence or absence of a sheet. Another type optically detects passage of a sheet when presence of the passing sheet blocks light from a light source.
However, the above-described control device requires added structure attaching the sensor. The additional structure complicates the device and makes provided a compact device difficult.
Feed rollers sometimes also function as thermal fixing devices for fixing toner onto sheets fed between two feed rollers. One of the feed rollers generates a high temperature. Toner on the transported sheet is melted by the high temperature and thereby fixed to the sheet. However, the high temperature can damage sensors that are disposed adjacent to the hot feed roller. Some sensors therefor can not be positioned too near the hot feed roller. This limits design options for feed rollers and associated sensors.